Help needed with AI generated texture
You should ask this question in computer graphic exchange.

Hiring some 3D artist for these job is a good option, seriously. If you find out the solution, Please submit your work to SIGGRAPH or any top-level conference. That's not an easy job for now but, yes, doable. And I don't think Blender can do anything for you except opening a finished 3D model or showing the result or provide a playground for 3D tweaking.

Answer for the question:

1. Normalize color among the set

A lot of work, just go searching "normalized color python".

2. Turn the set of real photos into a color texture.

Are the photo always take as the same angle? The animal type? If the photo has no obvious description point. It will be very hard to tell computer to recognize them. It's called feature mapping.

Also you will need to reconstruct the 3D model.

3. Extract the size parameters from the set

This is the most easiest part among these step. If you got Step.2 done correctly, you can directly know those 3-dimension coordinate of parts. Just calculate them using Euclidean distance.